U.S. patent application number 13/823587 was filed with the patent office on 2013-07-11 for display device.
This patent application is currently assigned to SHARP KABUSHIKI KAISHA. The applicant listed for this patent is Toshiyuki Fujine, Tomoharu Noutoshi. Invention is credited to Toshiyuki Fujine, Tomoharu Noutoshi.
Application Number | 20130176498 13/823587 |
Document ID | / |
Family ID | 45993723 |
Filed Date | 2013-07-11 |
United States Patent
Application |
20130176498 |
Kind Code |
A1 |
Noutoshi; Tomoharu ; et
al. |
July 11, 2013 |
DISPLAY DEVICE
Abstract
Provided is a display device compatible with RGBY, RGBW, and
other multiple primary color displays, wherein a desired luminance
ratio of primary colors to white can be obtained. The display
device comprises: a display panel that includes sub-pixels composed
of 4 or more primary colors; and a signal adjustment portion that
adjusts image signals composed of luminance signals and color
difference signals. The signal adjustment portion comprises: a
luminance gamma adjustment portion; a color gain adjustment portion
that increases the color gain of color difference signals, for
image signals for which the luminance levels of luminance signals
has been reduced; and a CMS portion that adjusts the gain for each
color component such that the luminance ratio of primary colors to
white becomes closer to a value that is determined in a
predetermined image signal format for image signals in which the
color difference signal gain has been increased.
Inventors: |
Noutoshi; Tomoharu;
(Osaka-shi, JP) ; Fujine; Toshiyuki; (Osaka-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Noutoshi; Tomoharu
Fujine; Toshiyuki |
Osaka-shi
Osaka-shi |
|
JP
JP |
|
|
Assignee: |
SHARP KABUSHIKI KAISHA
Osaka-shi, Osaka
JP
|
Family ID: |
45993723 |
Appl. No.: |
13/823587 |
Filed: |
October 21, 2011 |
PCT Filed: |
October 21, 2011 |
PCT NO: |
PCT/JP2011/074254 |
371 Date: |
March 14, 2013 |
Current U.S.
Class: |
348/712 |
Current CPC
Class: |
G09G 2300/0426 20130101;
H04N 9/67 20130101; H04N 9/87 20130101; G09G 3/3607 20130101; H04N
9/73 20130101; G09G 2300/0876 20130101; G09G 2300/0452 20130101;
G09G 2340/06 20130101; H04N 9/68 20130101 |
Class at
Publication: |
348/712 |
International
Class: |
H04N 9/87 20060101
H04N009/87 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2010 |
JP |
2010-239196 |
Oct 20, 2011 |
JP |
2011-230263 |
Claims
1-10. (canceled)
11. A display device comprising a display panel which displays a
video image using pixels that include sub-pixels composed of four
or more primary colors, further comprising a signal conditioning
portion which adjusts a video signal composed of a luminance signal
and a color difference signal so that the luminance ratio of
primary colors to white at the time of displaying a video image on
the display panel approaches the value that is determined in a
predetermined video signal format, wherein the signal conditioning
portion includes a luminance level adjustment portion which adjusts
gamma or gain of a luminance signal composing the video signal to
reduce a luminance level of the luminance signal; a first color
gain adjustment portion which increases color gain of the color
difference signal composing the video signal; and a second color
gain adjustment portion which adjusts gain for each color component
of the color difference signal.
12. The display device as defined in claim 11, wherein the signal
conditioning portion adjusts the luminance ratio of primary colors
to white at the time of displaying the video image on the display
panel according to a user operation.
13. The display device as defined in claim 11, wherein the first
color gain adjustment portion increases color gain of the color
difference signal composing the video signal for the video signal
in which the luminance level of the luminance signal is reduced by
the luminance level adjustment portion.
14. The display device as defined in claim 13, wherein the second
color gain adjustment portion adjusts gain for each color component
of the color difference signal and adjusts so that the luminance
ratio of primary colors to white approaches the value that is
determined in the predetermined video signal format for the video
signal in which the color gain of the color difference signal is
increased by the first color gain adjustment portion.
15. The display device as defined in claim 11, wherein the signal
conditioning portion includes an RGB/YCbCr conversion portion which
converts an RGB signal into an YCbCr signal when the RGB signal is
input; and a YCbCr/RGB conversion portion which converts the YCbCr
signal adjusted so that the luminance ratio of primary colors to
white approaches the value that is determined in the predetermined
video signal format into the RGB signal.
16. The display device as defined in claim 11, wherein the
luminance level of the luminance signal is reduced by the luminance
level adjustment portion so that white luminance on a screen of the
display panel is equal to or more than a predetermined value.
17. The display device as defined in claim 11, including a primary
color luminance ratio calculation portion which calculates the
luminance ratio of primary colors to white based on a result of
signal conditioning of each of the luminance level adjustment
portion, the first color gain adjustment portion and the second
color gain adjustment portion, wherein the signal conditioning is
allowed to be performed for each of the luminance level adjustment
portion, the first color gain adjustment portion and the second
color gain adjustment portion while displaying a calculation result
by the primary color luminance ratio calculation portion.
18. The display device as defined in claim 11, wherein the value
that is determined in the predetermined video signal format is a
luminance ratio of primary colors to white in ITU-R.BT 709
standard.
19. The display device as defined in claim 11, wherein the
sub-pixels included in the pixel include at least RGB three primary
colors, and the luminance ratio of primary colors to white is a
luminance ratio of the RGB three primary colors.
Description
TECHNICAL FIELD
[0001] The present invention relates to a display device, and more
particularly to a display device dealing with multi-primary color
display of RGBY, RGBW, and the like.
BACKGROUND OF THE INVENTION
[0002] As a display means for displaying information or a video
image, various types of displays have conventionally been
commercialized for forming an image using pixels. In a common
display, for example, one pixel is composed of sub-pixels (sub
pixels) of three primary colors comprised of red (R), green (G),
and blue (B), thereby performing color display. These sub-pixels
are normally realized by using a color filter. In such a color
display technique, expansion of a color reproduction range has
recently been examined in order to improve display quality.
[0003] On the other hand, a so-called multi-primary color display
has been developed, which is capable of expanding a region on a
chromaticity diagram (in the case of a chromatic color) and
improving luminance efficiency (in the case of white) by increasing
the number of primary colors to four or more with use of a new
color other than three primary colors. For example, Patent Document
1 describes an RGBW type liquid crystal display device capable of
displaying an image with appropriate luminance. The device is
configured, in determining luminance of a liquid crystal panel, to
separately and appropriately control luminance of pixels in a
transparent filter portion corresponding to white (W) based on
predetermined calculation, thereby improving luminance of an image
which is output from the liquid crystal panel.
PRIOR ART DOCUMENT
Patent Documents
[0004] [Patent Document 1] Japanese Laid-Open Patent Publication
No. 2001-154636
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0005] However, although the RGBW type liquid crystal display
device recited in the above-described Patent Document 1 allows
white luminance to be increased by adding W to RGB three primary
colors, luminance per sub-pixel is reduced compared to an RGB type
liquid crystal display device, and thus luminance of RGB three
primary colors is decreased. Such a problematic decreased primary
color luminance of a multi-primary color display will be described
below.
[0006] There are roughly two kinds of causes of the decreased
primary color luminance of a multi-primary color display, and the
first cause is that an aperture ratio is decreased, that is to say,
as the number of primary colors is increased, an area per one
sub-pixel is reduced, and luminance per sub-pixel is thus
decreased, accordingly. In this case, it is possible to increase
luminance by a method of increasing an aperture ratio of a liquid
crystal panel by raising drive voltage of a liquid crystal, a
method of increasing luminance of a backlight by changing current
supplied to a backlight or backlight duty, or the like.
Additionally, the second cause is that white balance changes, that
is to say, as the number of primary colors is increased, a
contribution ratio to white per one primary color is reduced, and
luminance per sub-pixel is thus decreased, accordingly.
[0007] For example, in the case of an RGB three-color system, when
maximum white luminance is 100, luminance of each primary color is
provided as, for example, R:20, G:70, and B:10 (R+G+B=100). On the
other hand, maximum white luminance of 100 in the case of an RGBW
four-color system results in, for example, R:10, G:35, B:5, and
W:50 (R+G+B+W=100), where a ratio of each primary color to white is
decreased, and thus primary colors are dimmed. Additionally, mixed
colors are different from colors intended by video image signals.
That is, balance between white and primary colors is changed and
luminance per sub-pixel is decreased.
[0008] FIG. 8 is a diagram for explaining difference in a luminance
ratio of primary colors to white between a three-primary-color
display and a four-primary-color display. FIG. 8(A) is a diagram
showing a ratio of primary color to white for a three-primary-color
display while FIG. 8(B) is a diagram showing an example of a ratio
of primary color to white for a four-primary-color display. When a
ratio of W to the other colors in four primary colors is different,
numerical values in FIG. 8(B) are different, accordingly. The
example of FIG. 8(A) shows a ratio of primary color to white for
RGB three primary colors based on ITU-R.BT 709 standard as one of
video signal formats, in which, when white luminance is 100%, the
luminance ratio of red (R) is 19%, the luminance ratio of green (G)
is 70%, and the luminance ratio of blue (B) is 11%.
[0009] On the other hand, the example of FIG. 8(B) shows a ratio of
primary color to white for RGB three primary colors in a
four-primary-color display, in which when white luminance is 100%,
the luminance ratio of red (R) is 12%, the luminance ratio of green
(G) is 33%, and the luminance ratio of blue (B) is 10%, and it can
be seen that the primary color luminance ratios of red (R) and
green (G) are lower compared to the case of the three-primary-color
display of FIG. 8(A). Thus, there is a problem that, when a
multi-primary color display of four primary colors or the like is
provided, a ratio of primary color to white is decreased compared
to a three-primary-color display.
[0010] The present invention has been devised in view of the
above-described circumstances, and an object thereof is to allow a
display device corresponding to multi-primary color display of
RGBY, RGBW, and the like to obtain a desired ratio of primary color
to white.
Means for Solving the Problem
[0011] To solve the above problems, a first technical means of the
present invention is a display device comprising a display panel
which displays a video image using pixels that include sub-pixels
composed of four or more primary colors, wherein a luminance ratio
of primary colors to white at the time of displaying a video image
on the display panel is a value adjusted so as to approach a value
that is determined in a predetermined video signal format.
[0012] A second technical means of the present invention is the
display device of the first technical means, further comprising a
signal conditioning portion which adjusts a video signal composed
of a luminance signal and a color difference signal so that the
luminance ratio of primary colors to white at the time of
displaying a video image on the display panel approaches the value
that is determined in a predetermined video signal format, wherein
the signal conditioning portion includes a luminance level
adjustment portion which adjusts gamma or gain of a luminance
signal composing the video signal to reduce a luminance level of
the luminance signal; a first color gain adjustment portion which
increases color gain of the color difference signal composing the
video signal; and a second color gain adjustment portion which
adjusts gain for each color component of the color difference
signal.
[0013] A third technical means of the present invention is the
display device of the second technical means, wherein the signal
conditioning portion adjusts the luminance ratio of primary colors
to white at the time of displaying the video image on the display
panel according to a user operation.
[0014] A fourth technical means of the present invention is the
display device of the second or third technical means, wherein the
first color gain adjustment portion increases color gain of the
color difference signal composing the video signal for the video
signal in which the luminance level of the luminance signal is
reduced by the luminance level adjustment portion.
[0015] A fifth technical means of the present invention is the
display device of the fourth technical means, wherein the second
color gain adjustment portion adjusts gain for each color component
of the color difference signal and adjusts so that the luminance
ratio of primary colors to white approaches the value that is
determined in the predetermined video signal format for the video
signal in which the color gain of the color difference signal is
increased by the first color gain adjustment portion.
[0016] A sixth technical means of the present invention is the
display device of any one of the second to the fifth technical
means, wherein the signal conditioning portion includes an
RGB/YCbCr conversion portion which converts an RGB signal into an
YCbCr signal when the RGB signal is input; and a YCbCr/RGB
conversion portion which converts the YCbCr signal adjusted so that
the luminance ratio of primary colors to white approaches the value
that is determined in the predetermined video signal format into
the RGB signal.
[0017] A seventh technical means of the present invention is the
display device of any one of the second to the sixth technical
means, wherein the luminance level of the luminance signal is
reduced by the luminance level adjustment portion so that white
luminance on a screen of the display panel is equal to or more than
a predetermined value.
[0018] An eighth technical means of the present invention is the
display device of any one of the second to the seventh technical
means, including a primary color luminance ratio calculation
portion which calculates the luminance ratio of primary colors to
white based on a result of signal conditioning of each of the
luminance level adjustment portion, the first color gain adjustment
portion and the second color gain adjustment portion, wherein the
signal conditioning is allowed to be performed for each of the
luminance level adjustment portion, the first color gain adjustment
portion and the second color gain adjustment portion while
displaying a calculation result by the primary color luminance
ratio calculation portion.
[0019] A ninth technical means of the present invention is the
display device of any one of the first to the eighth technical
means, wherein the value that is determined in the predetermined
video signal format is a luminance ratio of primary colors to white
in ITU-R.BT 709 standard.
[0020] A tenth technical means of the present invention is the
display device of any one of the first to the ninth technical
means, wherein the sub-pixels included in the pixel include at
least RGB three primary colors, and the luminance ratio of primary
colors to white is a luminance ratio of the RGB three primary
colors.
Effects of the Invention
[0021] According to the present invention, in a display device
corresponding to multi-primary color display of RGBY, RGBW, and the
like, it is possible to relatively change a ratio of primary color
to white by applying various types of signal conditioning
processing, thus making it possible to obtain a desired primary
color luminance ratio.
BRIEF DESCRIPTION OF DRAWINGS
[0022] FIG. 1 is a block diagram showing a configuration example of
a display device according to an embodiment of the present
invention.
[0023] FIG. 2 is a diagram schematically showing a configuration
example of a display portion.
[0024] FIG. 3 is a diagram showing a configuration example of each
sub pixel forming portion shown in FIG. 2.
[0025] FIG. 4 is a block diagram showing a configuration example of
a signal conditioning portion.
[0026] FIG. 5 is a diagram for explaining an example of a primary
color luminance ratio adjustment method by the signal conditioning
portion.
[0027] FIG. 6 is a diagram showing an example of correspondence
relation between a primary color luminance ratio and white
luminance when a luminance signal is compressed in a varied
ratio.
[0028] FIG. 7 is a diagram showing an example of a dialogue screen
for allowing a user to select luminance and a primary color
luminance ratio.
[0029] FIG. 8 is a diagram for explaining difference in a primary
color luminance ratio between a three-primary-color display and a
four-primary-color display.
PREFERRED EMBODIMENT OF THE INVENTION
[0030] Hereinafter, description will be given for preferred
embodiments according to a display device of the present invention
with reference to the accompanying drawings.
[0031] FIG. 1 is a block diagram showing a configuration example of
a display device according to an embodiment of the present
invention. As the display device in this example, an RGBY (red,
green, blue and yellow) type liquid crystal display device will be
described as a representative example, however, each of other
multi-primary color displays in an RGBW (red, green, blue and
white) type, an RGBC (red, green, blue and cyan) type, and the like
also has the same basic configuration. This liquid crystal display
device is roughly comprised of a drive control circuit 1, an input
portion 2, a signal conditioning portion 3, a control portion 4, a
light source control circuit 5, and a display portion 6. The
display portion 6 is provided with an active matrix type color
display panel, and the drive control circuit 1 generates a driving
signal for driving the display portion 6.
[0032] The input portion 2 is an external interface for connecting
a tuner for receiving a digital broadcast signal to input a video
signal included in the digital broadcast signal, or an external
equipment such as a game machine, a player, a recorder and a PC
(personal computer) to input the video signal from the external
equipment. The signal conditioning portion 3 is a circuit for
applying various types of signal conditioning processing to the
video signal input from the input portion 2. The control portion 4
is comprised of a CPU, a memory and the like for controlling
movement of the liquid crystal display device. Note that, the
signal conditioning portion 3 may be configured integrally with the
control portion 4. The light source control circuit 5 controls
electric power supplied to a backlight light source constituting
the display portion 6 in accordance with a control command from the
control portion 4 to adjust luminance of the backlight light
source.
[0033] The display portion 6 is comprised of a color filter 7, a
liquid crystal panel main body 8, and a backlight light source 9.
In the liquid crystal panel main body 8, as shown in FIG. 3
described below, a plurality of data signal lines Ls, and a
plurality of scanning signal lines Lg intersecting with a plurality
of the data signal lines Ls are formed. The liquid crystal panel
main body 8 and the color filter 7 constitute a color liquid
crystal panel including a plurality of pixel forming portions
arranged in a matrix state. The backlight light source 9 may be an
LED (Light Emitting Diode), a cold cathode fluorescent lamp (CCFL),
or the like, for example.
[0034] FIG. 2 is a diagram schematically showing a configuration
example of the display portion 6. Each pixel forming portion 62 at
the display portion 6 is comprised of an R sub pixel forming
portion 61, a G sub pixel forming portion 61, a B sub pixel forming
portion 61, and a Y sub pixel forming portion 61 corresponding to
red (R), green (G), blue (B) and yellow (Y), respectively, in which
each pixel of a color image displayed by the display portion 6 is
composed of an R sub pixel, a G sub pixel, a B sub pixel and a Y
sub pixel corresponding to red, green, blue and yellow,
respectively. Note that, the above sub pixel has the same meaning
as a sub-pixel. Hereinafter, sub pixels included in each pixel
contain at least three primary colors of red (R), green (G) and
blue (B), and a luminance ratio of the RGB three primary colors
will be illustrated as a ratio of primary color to white.
[0035] FIG. 3 is a diagram showing a configuration example of each
sub pixel forming portion shown in FIG. 2. FIG. 3 (A) is a diagram
showing an electrical configuration of one of the sub pixel forming
portions 61 in the display portion 6, and FIG. 3 (B) is an
equivalent circuit diagram showing an electrical configuration of
the sub pixel forming portion 61. As shown in FIG. 2 and FIG. 3,
each pixel forming portion 62 is comprised of the same number of
sub pixel forming portions 61 as the number of primary colors for
displaying a color image, and each sub pixel forming portion 61 is
provided corresponding to an intersection of a plurality of data
signal lines Ls and a plurality of scanning signal lines Lg.
Moreover, an auxiliary capacitance line Lcs arranged parallel to
each scanning signal line Lg is provided and a common electrode
Ecom common to all the sub pixel forming portions 61 is
provided.
[0036] In FIG. 3, each sub pixel forming portion 61 includes a thin
film transistor (TFT) 61a as a switching element having a gate
terminal connected to the scanning signal line Lg passing an
intersection corresponding thereto, as well as having a source
terminal connected to the data signal lines Ls passing the
intersection; a pixel electrode 61b connected to a drain terminal
of the TFT 61a; and an auxiliary electrode 61c arranged holding
with the pixel electrode 61b an auxiliary capacitance Ccs so as to
be formed therebetween. Further, each sub pixel forming portion 61
includes the common electrode Ecom commonly provided in all the sub
pixel forming portions 61, and a liquid crystal layer as an
electro-optic element held between the pixel electrode 61b and the
common electrode Ecom commonly provided in all the sub pixel
forming portions 61, in which a liquid crystal capacitance Clc is
formed from the pixel electrode 61b, the common electrode Ecom, and
the liquid crystal layer held therebetween.
[0037] The drive control circuit 1 is provided with a display
control circuit 11, a data signal line drive circuit 13 and a
scanning signal line drive circuit 14. The display control circuit
11 receives a data signal DAT (Ri, Gi, Bi) from the input portion 2
and a timing control signal TS from a not-shown timing controller,
and outputs a digital video signal DV (Ro, Go, Bo, Yo), a data
start pulse signal SSP, a data clock signal SCK, a latch strobe
signal LS, a gate start pulse signal GSP, a gate clock signal GCK,
and the like.
[0038] As shown in FIG. 2, each sub pixel forming portion 61 of the
display portion 6 is comprised of an R sub pixel forming portion, a
G sub pixel forming portion, a B sub pixel forming portion, and a Y
sub pixel forming portion corresponding to red, green, blue and
yellow, respectively, while the data signal DAT is composed of
three primary color signals corresponding to three primary colors
of red, green and blue (Ri, Gi, Bi), respectively. The display
control circuit 11 is provided with a converting circuit 12 for
converting the input primary color signals corresponding to RGB
three primary colors (Ri, Gi, Bi) into the output primary color
signals corresponding to four RGBY primary colors (Ro, Go, Bo, Yo).
The digital video signal DV is composed of the output primary color
signals (Ro, Go, Bo, Yo) to be output from the converting circuit
12, which allows to display a color image to be displayed on the
display portion 6.
[0039] Further, the above-described data start pulse signal SSP,
data clock signal SCK, latch strobe signal LS, gate start pulse
signal GSP, gate clock signal GCK and the like are timing signals
for controlling timing for displaying an image on the display
portion 6.
[0040] The data signal line drive circuit 13 receives the digital
image signal DV (Ro, Go, Bo, Yo), the data start pulse signal SSP,
the data clock signal SCK and the latch strobe signal LS output
from the display control circuit 11, and applies data signal
voltage Vs as a driving signal to each data signal line Ls for
charging pixel capacity (Clc+Ccs) in each sub pixel forming portion
61 in the display portion 6. At the time, in the data signal line
drive circuit 13, the digital video signal DV indicating voltage to
be applied to each data signal line Ls is sequentially held at the
time of generating a pulse of the data clock signal SCK. Then, at
the time of generating a pulse of the latch strobe signal LS, the
digital video signal DV described above is converted into analog
voltage to be concurrently applied to all the data signal lines Ls
in the display portion 6 as the data signal voltage Vs.
[0041] In the embodiment, the data signal line drive circuit 13
generates analog voltage corresponding to the primary color signals
Ro, Go, Bo and Yo which form the digital video signal DV as the
data signal voltage Vs, and applies the data signal voltage Vs
corresponding to the red primary color signal Ro to the data signal
lines Ls connected to the R sub pixel forming portion 61, the data
signal voltage Vs corresponding to the green primary color signal
Go to the data signal line Ls connected to the G sub pixel forming
portion 61, the data signal voltage Vs corresponding to the blue
primary color signal Bo to the data signal line Ls connected to the
B sub pixel forming portion 61, and the data signal voltage Vs
corresponding to the yellow primary color signal Yo to the data
signal line Ls connected to the Y sub pixel forming portion 61.
[0042] The scanning signal line drive circuit 14 sequentially
applies an active scanning signal (scanning signal voltage Vg for
turning on the TFT 61a) to the scanning signal line Lg in the
display portion 6 based on the gate start pulse signal GSP and the
gate clock signal GCK output from the display control circuit
11.
[0043] The drive control circuit 1 also includes auxiliary
electrode drive circuit and common electrode drive circuit
(not-shown). Predetermined auxiliary electrode voltage Vcs is
applied to each auxiliary capacitance line Lcs from the auxiliary
electrode drive circuit, and predetermined common voltage Vcom is
applied to the common electrode Ecom from the common electrode
drive circuit. Note that, the auxiliary electrode voltage Vcs and
the common voltage Vcom may be provided as the same voltage while
the auxiliary electrode drive circuit and the common electrode
drive circuit may be provided in common.
[0044] As described above, at the display portion 6, the data
signal voltage Vs, the scanning signal voltage Vg, the common
voltage Vcom and the auxiliary electrode voltage Vcs are applied to
the data signal line Ls, to the scanning signal line Lg, to the
common electrode Ecom and to the auxiliary capacitance line Lcs,
respectively. Thereby, voltage corresponding to the digital video
signal DV is held in pixel capacity of each sub pixel forming
portion 61 and applied to the liquid crystal layer. As a result, a
color image indicated by the digital video signal DV is displayed
on the display portion 6.
[0045] Note that, at the time, each R sub pixel forming portion 61
controls a transmission amount of red light corresponding to
voltage held in pixel capacity inside thereof; each G sub pixel
forming portion 61 controls a transmission amount of green light
corresponding to voltage held in pixel capacity inside thereof;
each B sub pixel forming portion 61 controls a transmission amount
of blue light corresponding to voltage held in pixel capacity
inside thereof; and each Y sub pixel forming portion 61 controls a
transmission amount of yellow light corresponding to voltage held
in pixel capacity inside thereof.
[0046] A main characterizing part of the present invention is to
allow a desired ratio of primary color to white to be obtained in
the display device corresponding to multi-primary color display of
RGBY, RGBW, and the like. That is, the ratio of primary color to
white at the time of displaying a video image on the display
portion 6 is rendered a value adjusted so as to approach a value
that is determined in a predetermined video signal format. As a
configuration therefor, as shown in FIG. 4, the signal conditioning
portion 3 is provided with a gain adjustment portion 32, and the
gain adjustment portion 32 is provided with a luminance gamma
adjustment portion 33 as an example of a luminance level adjustment
portion reducing a luminance level of a luminance signal
constituting a video signal. Note that, the luminance level
adjustment portion may be not limited to the luminance gamma
adjustment portion 33 for adjusting gamma of a luminance signal,
and be a luminance gain adjustment portion for adjusting a gain of
a luminance signal.
[0047] Further, the signal conditioning portion 3 is provided with
a color gain adjustment portion 34 corresponding to a first color
gain adjustment portion that increases a color gain of a color
difference signal forming the video signal for the video signal
having the luminance level of the luminance signal reduced at the
luminance gamma adjustment portion 33, and a CMS (color management
system) portion 35 corresponding to a second color gain adjustment
portion that adjusts a gain for each color component of the color
difference signal constituting the video signal so that the ratio
of primary color to white approaches a value determined in a
predetermined video signal format for the video signal having the
color gain of the color difference signal increased at the color
gain adjustment portion 34. Note that, regarding the
above-described processing order, the video signal is standardized
also inside the CPU, and if a color gain is increased before
reducing a luminance level of a luminance signal, namely, before
compressing a luminance signal, clipping (failure) may be caused.
Therefore, it needs to compress a luminance signal at the beginning
of a series of processing. However, processing of the color gain
after luminance signal compression may be performed before or after
processing of the CMS, which is not limited to the above-described
order.
[0048] In the present invention, for example, a user operates a
remote control R to perform signal conditioning by the luminance
gamma adjustment portion 33, the color gain adjustment portion 34
and the CMS portion 35, and adjusts so that the ratio of primary
color to white at the time of displaying a video image on the
display portion 6 approaches a value that is determined in a
predetermined video signal format. The value determined in the
predetermined video signal format is, for example, a ratio of
primary color to white in the ITU-R.BT 709 standard, and also
referred to as a target value in description below.
[0049] Note that, signal conditioning processing according to the
present invention may be not limited to operation by a user, and
allowed to be automatically executed according to an image quality
mode, an input signal type, a program genre, and the like. For
example, some display devices are allowed to set a plurality of
image quality modes for adjusting a display video image quality.
These image quality modes are set in consideration of a viewing
environment of the display device, a user's request, and the like.
For example, a "dynamic (over-the-counter) mode", a "standard
(normal) mode", a "movie mode", a "game mode" and the like are set.
These image quality modes, details of setting of these modes and
the like are determined by a manufacturer of a display device, and
additionally, names of the modes are not standardized, in which
various types of mode names are used for respective
manufacturers.
[0050] In the present invention, signal conditioning may be
performed according to an image quality mode to allow video image
display at a primary color luminance ratio that is most suitable
for the image quality mode. Specifically, for each image quality
mode, a sequence of primary color luminance ratio adjustment
processing may be performed by the luminance gamma adjustment
portion 33, the color gain adjustment portion 34 and the CMS
portion 35 to store the adjustment results in a memory (not-shown)
for each image quality mode. For example, in the case of the
"dynamic (over-the-counter) mode" and the "movie mode", the ratio
of primary color to white may be increased to a certain level since
a primary color is possibly desired to be exhibited more vividly.
Accordingly, an adjustment amount of the primary color luminance
ratio may be increased more than that of a primary color luminance
ratio in other image quality modes.
[0051] Moreover, some display devices are connected to a game
machine, a PC (personal computer) or the like in addition to a
tuner for receiving a digital broadcast signal to allow a video
signal input from the game machine, a video signal input from the
PC or the like to be displayed. In the present invention, signal
conditioning may be performed according to a type of an input video
signal (a television video signal, a game video signal and a PC
video signal) so as to allow display of a video image at a primary
luminance ratio that is most suitable for the input video signal.
In a case where an input video signal is a PC video signal or a
game video signal, the ratio of primary color to white may not be
increased so much because of including many colors of relatively
low color saturation. Accordingly, an adjustment amount of the
primary color luminance ratio may be decreased more than that of a
primary color luminance ratio in a case where the input video
signal is a television video signal.
[0052] Further, program genre information of a "movie", a "sport"
and the like are added to a digital broadcast signal. In the
present invention, signal conditioning may be performed according
to a program genre of an input video image so as to allow display
of the video image at a primary color luminance ratio that is most
suitable for the program genre of the input video image. For
example, in a case where the program genre of the input video image
is a "movie", the ratio of primary color to white may be increased
to a certain level since a primary color is possibly desired to be
exhibited more vividly. Accordingly, an adjustment amount of the
primary color luminance ratio may be increased more than that of a
primary color luminance ratio in the case of other program
genres.
[0053] In the embodiment, the signal conditioning portion 3 is
provided with, in a case where the RGB signal is input, an
RGB/YCbCr conversion portion 31 for converting the RGB signal into
a YCbCr signal, and the luminance gamma adjustment portion 33
inputs the YCbCr signal converted at the RGB/YCbCr conversion
portion 31 to adjust gamma of a luminance signal constituting the
YCbCr signal, thereby reducing a luminance level of the luminance
signal. Further, the signal conditioning portion 3 is provided with
a YCbCr/RGB conversion portion 36 for converting the YCbCr signal
after a user adjusts the ratio of primary color to white at the
gain adjustment portion 32 into the RGB signal. That is, processing
at the luminance gamma adjustment portion 33, the color gain
adjustment portion 34 and the CMS portion 35 is executed for a
luminance signal (Y) and a color difference signal (CbCr) forming
the YCbCr signal.
[0054] FIG. 5 is a diagram for explaining an example of a primary
color luminance ratio adjustment method by the signal conditioning
portion 3. In the video signals (Ro, Go, Bo, Yo) converted by the
converting circuit 12, as shown in the above-described FIG. 8(B),
when maximum white (W) luminance is 100%, the luminance ratio of
primary colors to white (W) is R:G:B=12%:33%:10%, which shows that
the ratio each for red (R) and green (G), in particular, becomes
lower compared to the primary color luminance ratio
(R:G:B=19%:70%:11%) of the ITU-R.BT 709 standard shown in FIG.
8(A). Therefore, in this example, based on the primary color
luminance ratio (R:G:B=19%:70%:11%) on the standard as a target
value, a primary color luminance ratio (R:G:B=12%:33%:10%) in
four-primary-color display is adjusted.
[0055] When a luminance signal is greatly lowered in this case,
small amplification is enough for color gain, however, in such a
case, sufficient white luminance may not be able to be secured. On
the contrary, when a luminance signal is not greatly lowered and
white luminance is prioritized, amplification of color gain needs
to be increased. However, since a color signal has a limited
numerical value from 0 to 255, an amplification amount of a color
signal is limited, and thus a desired primary color luminance ratio
is not allowed to be secured in some cases. Therefore, the signal
conditioning portion 3 makes it possible to obtain a desired
primary color luminance ratio while securing a certain level of
white luminance only by signal conditioning by executing processing
of relatively increasing a primary color luminance ratio by
lowering a luminance signal to a certain level and decreasing white
luminance and processing of adjustment of a primary color luminance
ratio by color gain adjustment for adjusting gain of entire color
components and the CMS for adjusting gain for each color
component.
[0056] Note that, the display device includes a primary color
luminance ratio calculation portion for calculating a luminance
ratio of primary colors to white at the time of displaying a video
image on the display portion 6 based on a result of signal
conditioning of each of the luminance gamma adjustment portion 33,
the color gain adjustment portion 34, and the CMS portion 35, and
is configured to be able to perform signal conditioning of each of
the luminance gamma adjustment portion 33, the color gain
adjustment portion 34, and the CMS portion 35. A function as the
primary color luminance ratio calculation portion is realized by
the control portion 4. Specifically, for example, a conversion
equation for converting a YCbCr signal composed of a luminance
signal and a color difference signal into each of RGBY (red, green,
blue, and yellow) primary color signal may be stored in advance in
a memory (not-shown) in the control portion 4.
[0057] In FIG. 5(A), the luminance gamma adjustment portion 33
adjusts gamma of the luminance signal in the YCbCr signal converted
by the RGB/YCbCr conversion portion 31 to reduce a luminance level.
The processing is realizable by displaying OSD (On Screen Display)
for adjusting gamma of a luminance signal, and operating the remote
control R by a user. Note that, a luminance ratio of primary colors
to white is changed corresponding to adjustment of a luminance
level, however the primary color luminance ratio at the time is
calculated by the control portion 4, and a result of which is
displayed by the OSD. For example, when maximum white (W) luminance
of 100% in FIG. 8(B) is lowered by 20% to 80%, a luminance ratio of
green (G) having a large amount of a luminance component is
decreased from 33% to 28%, while luminance ratios of red (R) and
blue (B) each having a small luminance component are decreased from
12% to 11.5% in red (R) and from 10% to 9.8% in blue (B), and thus
there is little change in this example.
[0058] Further, the luminance gamma adjustment portion 33
standardizes white (W). This is processing for regarding 80% as
100% in order to make a luminance level 80% serve as a standard for
convenience. Along with this standardization, a primary color
luminance ratio of RGB is changed. Specifically, the percentages
are changed from 11.5% to 14.3% in red (R), from 28% to 35% in
green (G), and from 9.8% to 12.3% in blue (B).
[0059] Next, in FIG. 5 (B), the color gain adjustment portion 34
adjusts color gain of a color difference signal in the YCbCr signal
so as to be increased, which is realizable by displaying OSD (On
Screen Display) for adjusting color gain of a color difference
signal, and operating the remote control R by a user. Note that,
corresponding to adjustment of color gain, a luminance ratio of
primary colors to white is changed, and the primary color luminance
ratio at the time is calculated by the control portion 4, a result
of which is displayed by the OSD. A primary color luminance ratio
of RGB is thereby raised, however, red (R) and blue (B) not
including so much of luminance component are saturated by
increasing color gain, and luminance ratios of which may be too
high. The example of FIG. 5(B) shows that luminance ratios are
18.6% for red (R), 41% for green (G), and 15.1% for blue (B), and a
luminance ratio of blue (B) is higher than a target value
(11%).
[0060] Next, in FIG. 5(C), the CMS portion 35 adjusts gain for each
color component of a color difference signal in the YCbCr signal,
which is realizable by displaying OSD (On Screen Display) for
adjusting gain for each color component of the color difference
signal, and operating the remote control R by a user. Note that, a
luminance ratio of primary colors to white is changed corresponding
to gain adjustment for each color component, however, the luminance
ratio of primary colors is calculated by the control portion 4,
which result is displayed on the OSD display. This CMS processing
is a known technique as recited, for example, in Japanese Laid-Open
Patent Publication No. 2004-64198, which specific description is
omitted herein. Generally, in a CMS, a settable range is small and
color noise is generated as largely moved, therefore, color gain is
increased uniformly by the color gain adjustment portion 33, and
thereafter fine adjustment is performed for each hue in the
CMS.
[0061] In the example of FIG. 5(B), a luminance ratio of red (R) is
18.6%, and obtained as a value which approximates an almost target
value (19%) is obtained, while having a luminance ratio of green
(G) of 41% which is insufficient for a target value (70%) as well
as a luminance ratio of blue (B) of 15.1% which is too high for a
target value (11%). Accordingly, as shown in FIG. 5(C), the CMS
portion 35 is used to perform fine adjustment of gain of red (R) so
as to change the luminance ratio to the target value of 19%, to
increase gain of green (G) so as to change the luminance ratio to
56%, and to decrease gain of blue (B) so as to change the luminance
to the target value of 11%.
[0062] In this example, the luminance value of green (G) is 56% and
slightly shifted from the target value of 70% due to trade-off
relation between a primary color luminance ratio and white
luminance. This will be specifically described based on FIG. 6.
[0063] FIG. 6 is a diagram showing an example of correspondence
relation between a primary color luminance ratio and white
luminance when a luminance signal is compressed in a varied ratio.
The example of FIG. 6 shows a measured value of white luminance and
a primary color luminance ratio on each screen where a primary
color luminance ratio in a 100% luminance signal is
R:G:B=12%:33%:10%, and the luminance signal is lowered to 60%, 70%,
and 80%. Note that, white luminance on the screen (hereinafter,
referred to as screen white luminance) was measured with a
luminance meter (spectroradiometer for ultra-low luminance SR-UL1R,
manufactured by Topcon Technohouse Corporation). Additionally, a
target value of a primary color luminance ratio is set to a primary
color luminance ratio based on the ITU-R.BT 709 standard
(R:G:B=19%:70%:11%).
[0064] In FIG. 6, as a first example, when a luminance signal is
lowered to 60%, a measured value of screen white luminance is 144
cd/m.sup.2, and a primary color luminance ratio is adjusted to
R:G:B=19%:72%:11%. Moreover, as a second example, when the
luminance signal is lowered to 70%, a measured value of screen
white luminance is 210 cd/m.sup.2, and a primary color luminance
ratio is adjusted to R:G:B=19%:70%:11%. Further, as a third
example, when the luminance signal is lowered to 80%, a measured
value of screen white luminance is 284 cd/m.sup.2, and a primary
color luminance ratio is adjusted to R:G:B=19%: 56%:11%.
[0065] As described above, in the first and second examples,
although the primary color luminance ratio is obtained as
approximately the same value of the ITU-R.BT 709 standard, a
luminance level of the luminance signal is greatly reduced
relatively, and thus the screen white luminance is rather
insufficient. On the other hand, in the third example, although the
primary color luminance ratio is slightly shifted from that of the
ITU-R.BT 709 standard, a luminance level of the luminance signal is
not greatly reduced, thus having white luminance of 280 cd/m.sup.2
or more, which is common in viewing at home. Accordingly,
sufficient screen white luminance may be obtained. It is possible
to obtain a luminance ratio which is close to a desired primary
color luminance ratio while securing screen white luminance to a
certain level by performing signal conditioning as the third
example. In this manner, a luminance level of a luminance signal
may be reduced by adjusting gamma so that white luminance on a
screen is a predetermined value or more (for example, 280
cd/m.sup.2 or more) with use of the luminance gamma adjustment
portion 33.
[0066] As describe above, an RGB signal having a luminance ratio of
primary colors to white adjusted by the signal conditioning portion
3 is transmitted to the converting circuit 12 at a later stage, and
the RGB signal from the signal conditioning portion 3 is converted
into an RGBY signal to be output to the display portion 6 in the
converting circuit 12. At the time, a luminance ratio of primary
colors to white is adjusted to a desired value in the RGBY signal,
and thus, for example, it is possible to obtain a primary color
luminance ratio which is similar to that of the ITU-R.BT 709
standard also in four-primary-color display.
[0067] Note that, although description has so far been given for
the case where a luminance ratio of primary colors to white of R
(red), G (green), and B (blue) is adjusted, also for primary colors
other than those colors, for example, Y (yellow), C (cyan), and M
(magenta), it is possible to adjust a luminance ratio of primary
colors to white at the time of displaying a video image on the
display portion 6.
[0068] Hereinabove, the primary color luminance ratio adjustment
method by the RGBY type liquid crystal display device has been
described, and for example, before product shipment, a series of
primary color luminance ratio adjustment processing may be
performed by the luminance gamma adjustment portion 33, the color
gain adjustment portion 34, and the CMS portion 35 so as to store
an adjustment result thereof as default setting in a memory
(not-shown). Thus, after product shipment, a user is able to view a
video image with an optimal luminance ratio of primary colors to
white without need for performing the primary color luminance ratio
adjustment processing.
[0069] FIG. 7 is a diagram showing an example of a dialogue screen
for allowing a user to select luminance and a primary color
luminance ratio. For example, each maximum white (W) luminance may
be associated with a luminance ratio of primary colors to white (W)
to be held as a data table as the above-described adjustment result
at a design phase. When a primary color luminance ratio with
maximum white (W) luminance of 100% is R:G:B=12%:33%:10%, according
to the example of FIG. 6, a primary color luminance ratio with
maximum white (W) luminance of 80% is R:G:B=19%:56%:11%, and a
primary color luminance ratio at maximum white (W) luminance of 70%
is R:G:B=19%:70%:11%.
[0070] A user, when desiring to change a luminance ratio of primary
colors to white (W), is able to display the dialogue screen of FIG.
7, and select desired maximum luminance and a primary color
luminance ratio from the dialogue screen. Specifically, the user
may select "maximum luminance of 100%, brightness is prioritized"
when desiring to prioritize brightness. In this case, a primary
color luminance ratio is R:G:B=12%:33%:10%, so that a video image
is bright, but has low color saturation of red (R) and green (G).
Additionally, when color fidelity is desired to be added to
brightness, "maximum luminance of 80%, color fidelity is added" may
be selected. In this case, a primary color luminance ratio is
R:G:B=19%:56%:11%, and thus brightness is slightly decreased, but
color saturation of green (G) is increased, thereby making it
possible to obtain a video image with color saturation which is
close to that of the ITU-R.BT 709 standard. Further, when color
fidelity is desired to be prioritized, "maximum luminance of 70%,
color fidelity is prioritized" may be selected. In this case, a
primary color luminance ratio is R:G:B=19%:70%:11%, and thus
brightness is decreased, but color saturation of green (G) is
further increased, thereby making it possible to obtain a video
image with color saturation conforming to that of the ITU-R.BT 709
standard.
EXPLANATIONS OF LETTERS OR NUMERALS
[0071] 1 . . . drive control circuit; 2 . . . input portion; 3 . .
. signal conditioning portion; 4 . . . control portion; 5 . . .
light source control circuit; 6 . . . display portion; 7 . . .
color filter; 8 . . . liquid crystal panel main body; 9 . . .
backlight light source; 11 . . . display control circuit; 12 . . .
converting circuit; 13 . . . data signal line drive circuit; 14 . .
. scanning signal line drive circuit; and 15 . . . remote control
light-receiving portion.
* * * * *